The G360 Fractured Rock Observatory (FRO): a borehole network in Silurian dolostone to advance hydrogeologic insights, method development & collaborations

Jonathan Munn, Beth Parker, Peeter Pehme, Carlos Maldaner

Dans les comptes rendus d’articles de la conférence: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNC

ABSTRACT: This study presents insights from the G360 Fractured Rock Observatory on the University of Guelph campus in Guelph, Ontario, Canada, built to better understand flow through the regionally important dolostone aquifer and to test new borehole tools and techniques through collaboration. This research station includes a cluster of 9 continuously cored bedrock boreholes (6 vertical, and 3 inclined) in a 75 x 75 m area. The boreholes are drilled to a vertical depth of 73 m where they terminate in the Cabot Head Formation at the base of the Silurian dolostone aquifer sequence. Each borehole has been well characterized with core logging to capture lithology and fracture information, and extensive borehole testing including a large suite of borehole geophysical logs, depth-discrete packer testing, borehole dilution testing and FLUTeTM transmissivity profiling. The site is ideal for testing new technologies and methods with comparison to established methods. Specifically, we have tested and refined the fibre optic Active Distributed Temperature Sensing (A-DTS) method deployed with FLUTeTM liners for identifying and quantifying depth discrete flow direction and magnitude. Each borehole has a dedicated fibre optic cable, and the boreholes are connected at the surface with a trenched cable (1,751 m total) to allow simultaneous temperature measurements at hundreds of depths in 8 of the 9 boreholes. The A-DTS data demonstrates highly variable flow magnitude and direction through the vertical sequence, with flow occurring primarily in fractures, and some flow through dissolution channels. Hydraulic gradient and the A-DTS data demonstrate drastic flow direction changes with depth suggesting hydraulic influence of a nearby river and buried bedrock valley. The location on the University of Guelph campus, interesting hydrogeological setting, and the diversity of collected datasets make the FRO an excellent avenue for advancing the science, hands-on education, public outreach, and collaborations to develop new technologies.

Please include this code when submitting a data update: GEO2021_418

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